Motor controlled throttling poppet valve

Abstract

A motor controlled poppet valve is provided of the type including a valve body, a valve seat mounted at one end of the valve body, and a valve element that comprises a threaded shaft having one end engaged to a nut driven by a stepper motor, and a free end reciprocably moveable into a valve opening or a valve closing position, wherein the free end of the shaft assumes a substantially nonvarying distance from the drive nut or the stepper motor when moved into the valve closing position, and a resilient linkage assembly including a constant force spring that interconnects the free end of the shaft with the valve element. The resilient linkage forcibly depresses the valve element into the valve seat when the shaft is moved into the valve closing position with a force that remains substantially constant regardless of variations in the distance between the free end of the shaft and the valve closing position due to thermal expansion and contraction of the valve body. Additionally, the extreme control of the extent to which the valve element is moved toward the valve seat afforded by the combination of the stepper motor and threaded shaft allows the poppet valve to perform not only a gas isolation function, but throttling and soft start functions as well, thereby obviating the need for separate throttling or soft start valves in a vacuum system.